Centrifugal speed regulator for a surface working device



March 3, 1964 e. M. MAGARIAN 3,122,765

CENTRIFUGAL SPEED REGULATOR FOR A SURFACE WORKING DEVICE Filed May 4,1962 4 Sheets-Sheet l IN VEN TOR.

March 3, 1964 Filed May 4, 1962 G. M. MAGARIAN CENTRIFUGAL. SPEEDREGULATOR FOR A SURFACE WORKING DEVICE 4 Sheets-Sheet 2 Gama JV.MAGARIAAQ w I INVENTOR.

25AM V6444;

March 3, 1964 e. M. MAGARIAN 3,122,765

CENTRIFUGAL SPEED REGULATOR FOR A SURFACE WORKING DEVICE Filed May 4,1962 4 Shee ts-Sheet s 6"EQA 1. U M. MAGAQ/AM,

IN V EN TOR.

BY bi),

March 3, 1964 G. M. MAGARIAN 3,122,765

CENTRIFUGAL SPEED REGULATOR FOR A SURFACE WORKING DEVICE Filed May 4,1962 '4 Sheets-Sheet 4 '1 I "4 I l 4/ 4 47 46 4&4 5;

/ l-n g I fl/ I i 5' 4 4 9 INVENTOR.

6524 0 M. MAAE/A/V,

United States Patent Mail 3,122,765 CENTRIFUGAZL SEEED REGULATQR FOR ASURFACE WUPEQNG DEVICE Gerald M. Magarian, Long Beach, Calif, assignorto Preco, Incorporated, lies Angeles, Qalif, a corporation of CaliforniaFiled May 4, 1962, Ser. No. 192,499 6 Claims. (Q1. 15-49) The presentinvention relates generally to a surface Working machine designed topolish, scrub, or otherwise work on a plane surface; and,illustratively, the invention relates to a device, such as a floorpolisher, which is driven by an air motor and which is connectible tothe suction wand of an ordinary vacuum cleaner in order to induce acurrent of air through the air motor of the surface working device. Suchan air motor is illustrative of a power source whose speed varies Widelyunder varying load or varying power supply.

Since the present invention has been embodied in a device which isparticularly suited to floor polishing, the invention is illustrated anddescribed in this aspect; but it will be realized that other surfaceworking implements can replace the polishing brush. For example, thepolishing brush or buffer can be replaced by a brush for scrubbing, andabrasive element for sanding, or other suitable element for working onthe plane surface.

The familiar vacuum cleaner for household use has a fan or blower whichis driven by an electric motor. The air stream is drawn into the cleanerthrough the wand and flexible hose. The air stream is a convenientsource of power for an accessory, such as a floor polisher, connected tothe suction wand of the vacuum cleaner equ pment. The floor polisher, orother surface working device when driven by an air turbine operates mosteffectively within a relatively limited speed range since the turbine isadapted to operate most efiiciently at a given revolutionary speed.Although the optimum speed for the air turbine is determined in generalby the design of the particular unit, it will also differ for a givenunit at different rates of air flow; but for a given unit operating on aparticular air flow there is an optimum speed of rotation and for bestperformance the unit should be operated relatively close to that optimumspeed. Obviously, this indicates that a generally constant speed of thesurface working member, the polishing brush in the case of a floorpolisher, is desirable, as long as the air flow is constant. For higheror lower air flows, as produced by vacuum cleaners of high or low power,the generally constant speed should be somewhat higher or lower,respectively.

Obtaining a relatively constant speed of rotation of the workingelement, particularly in the case of a floor polisher which operates onsurfaces having different coefficients of fiiction, presents someproblems. The drag or frictional load on the Working unit varies greatlydepending upon the characteristics of the surface being worked on. Thisis true not only of different surfaces on which the unit may be operatedbut also it is true of the same surface with the passage of time, as forexample, a floor being waxed has a much lower coefficient of frictionand consequently much less drag on the working ele ment when the waxapplied to the floor is hardened and is polished than at the beginningof the operation.

Thus it is a general object of the invention to provide a surfaceworking machine powered by a variable speed motor such as an air turbinewhich operates best at a generally constant rotational speed.

More particularly, it is an object of the present invention to provide asurface working machine of this character having novel means for varyingthe downward pressure on the working element in a manner to compensatefor changes in the coefficient of the friction of the surface beingworked upon, for the purpose of maintaining a generally constant torqueload on the surface working element.

These objects of the invention are achieved in a surface working machineof this character by providing in combination: a variable speed motor; adrive member rotatably mounted on a supporting frame and driven by themotor; a surface working member rotatably connected with the drivemember and mounted concentrically thereof to rotate therewith and alsofor limited angular and axial movement relative to the drive member;centrifugally responsive means rotatably connected with the drive memberand tending to move to different positions relative thereto in responseto both the torque load on the brush and different centrifugal forces atdifferent rotational speeds of the drive member; means connecting thecentrifugally responsive means to the surface working member to rotatethe surface working member and the drive member in unison and also torotate the surface working member relative to the drive member inresponse to movement of the centrifugally responsive means, which isresponsive as above; and means including cooperating element on thedrive member and the surface working member acting to press the surfaceworking member toward a working surface with more or less force as aresult of said relative rotational movement of the surface workingmember and the drive member. As a result of this arrangement, agenerally constant rotational speed of the surface working member andmotor is maintained with varying coeflicients of friction between thesurface and the surface working member.

How the above objects and advantages of the present invention, as wellas others not specifically mentioned herein are attained will be morereadily understood by reference to the following description and to theannexed drawings, in which;

FIG. 1 is a small-scale plan view of a surface working machine embodyingthe present invention.

FIG. 2 is an enlarged vertical section thereof on line 2-2 of FIG. 1;FIG. 2 being at full scale of a present embodiment.

FIG. 2a is an enlarged portion of FIG. 2 but differing in that thesurface working member is shown at its tippermost position.

FIG. 3 is a fragmentary horizontal section on line 3-3 of FIG. 2 showingthe bearing sleeve and the centrifugal weights in the positions occupiedat the inward end of the range of movement of the weights.

FIG. 4 is a diagrammatic developed view of the cooperating cam surfacespressing the surface working member down, showing the relative positionsthese members occupy when the working member is in an upper position.

FIG. 5 is an exploded view showing the hub carrying the drive member,the sleeve mounted thereon for carrying the surface working member, andthe connection between the sleeve and the centrifugally responsivemembers, the parts being separated for purposes of illustration.

FIG. 6 is a fragmentary horizontal section similar to FIG. 3 but showingthe centrifugal weights at the outward end of their range of movement.

FIG. 7 is a diagrammatic View similar to FIG. 4 but showing the camsurfaces at the opposite end of their range of relative movement, whenthe surface working element is pressed down.

FIG. 8 is a bottom plan of the surface working machine, viewed on line38 of FIG. 2.

Referring now to the drawing, there is shown a preferred embodiment ofthe present invention in the form of a floor polisher, seen in plan inFIG. 1. FIG. 2 is a median section through the device taken on avertical 'dirt under the polisher' from entering the turbine. hollowflexible bumper 14. is preferably mounted around the lower periphery ofcover 12 in order to prevent dam V the floor Polisher.

3 plane, showing a normal or median position of the sur face workingmember when the device is resting on the floor in the usual operationalposition.

The major assemblies. of the device seen in FIG. 2 are the frame A whichserves as a support structure for the various moving parts; the airturbine B which drives the surface working member C which is rotatablymounted upon the underside of a frame A to engage thefloor surface, asillustrated; and a drive member D, rotatable on the frame concentricallywith the surface working memher. The drive member D transmits power tothe surface working member through means that includes centrifugaily andbrush torque responsive means E seen best in FIGS. 3 and 6, thesecentrifugal means being rotatatable with the drive member as will befurther described. Cooperating elements, typically inclined camsurfaces, on hub 46 of the drive member D and sleeve 55 of the surfaceworking member C cooperate to press the latter downwardly against thefloor surface with a variable force, as a result of the relativerotational movement of .the surface working and drive members, caused bythe centrifugal means and in such a way as to compensate for changes inthe coefficient of friction encountered by the surface working memberand variable driving torque available from the air motor. Thus there ismaintained a generally constant load on the motor, assuming constant airflow power applied to it.

Any motor that, like an air turbine, changes speed with variations ofthe power supply or the torque load on the motor maybe considered to bea variable speed motor as the term isused herein.

Considering now the illustrative construction in greater detail, frame Acomprises several individual parts which are fastened together in anysuitable manner. Frame A includes a hollow domed housing 12' closed onits open underside by bottom plate which carries around its margin anarrow stationary brush 11, as seen in FIGS. 2 and 8, which engages thefloor surface and normally supports the Whole device on the floor,carrying a variable fraction of the entire weight of the floor polisheras will appear. Housing 12 is spaced upwardly above the bottom plate toenclose between them the interior-space containing the other parts ofthe frame, more especially two 'mag'or separable frame elements 15 and16 which'enclose and support bearings for the air turbine B and thedrive member D. Frame element 16 extends forwardly at 31 to form atleast in part an exhaust air duct at the forward end of which is anintegral collar 45 supporting shaft 44 on which the drive member D andthe surface working member C are rotatably mounted. Frame elements 15'and 16, bottom plate 10, and housing 12 are all secured together bymembers not shown, 'but may be 7 fastened together in any suitable way;Peripheral brush 1-1 will beseen to support the device, takinga part ofthe total weight as will appear. Plate 10 prevents air and A age tofurniture, walls, and the like from contact with The bearing supportstructures 15 and 16 are verticall separable and. provide bearingsupporting structure for journal bearings at team 19, as may be seen inFIG. 2.

These bearings are respectively at the upper and lower ends of thevertically disposed shaft Zil of air turbine B. Mounted on shaft Ztl isturbinewheel 22 which comprises an annular series ofblades'23 disposedconcentrically around; shaft 2 9. Blades 23 terminateat their innerends, at a positionv spaced from the hub ofjturbine wheel 22, allowingthe air'after inwardly passingbetween the blades to discharge upwardlyand axially of the turbine wheel. 7 7 V Surrounding moving blades 23 ofthe turbine wheel,

is an annular series of fixed blades 25 which are supported by framemember '15 and are positioned to direct air against the moving blades23. Air passes between fixed blades 25 by entering the blades from theinterior space between housing 12 and bottom plate 10. Admission tothis'interior space from the surrounding atmosphere is through an airintake opening at 27 in cover 12.

A stationary diaphragm 23 is mounted on the bearing support structure 15immediately beneath the turbine wheel 22 and has a small runningclearance with the hub of the turbine wheel in order to confine air flowto entering only through fixed blades 25. A ring 2? mounted on the upperedges of blades 23 confines air movement after discharge from fixedblades 25 to substantially a radial direction through the moving blades23 Air exhausted from the turbine leaves the floor polisher through anair duct. built in two sections 31 and 32;. The first section 31 isfixed in place and may be an integral portion of the bearing supportstructure 16 in order to provide a continuous enclosed path for airleaving the turbine to flow into the duct 31. A removable plate 31acloses the bottom of duct section 31. At the outlet'end, of duct 31 isswingingly mounted by shaft 33 a movable duct section 32 which isdesigned to take one end of a wand or hose connected at the other endtoa vacuum cleaner to induce air flow through the floor polisher over thepath described. Y

Lubrication for each of the journal bearings 18, and 19 is provided byoil saturated wicks 35 and 36 respectively which are located in wells inthe bearing support structures 16 and 15 respectively. These wells areeach covered over by a thin metal cap 37'which is press fitted to sealthe wicks in place and prevent the entryof dirt or other foreign'matterinto the well. These well spaces, are each connected to the shaft sideof their respective bearings by means of pressure equalizing openings 38so that air pressures within the wells are the same as pressures at theshaft side of the bearings to assure normal lubricant supply from'thewick to the bearings.

The hub ofturbine wheel 22 extends downwardly be low the blades. Theextension is in the form of an in-' tegral drive pinion with gear teeth46: which mesh with gear teeth 41 of a rim 54 around the peripheryofplate 52 of drive member D to drive the latter. Drive member D- isrotatably supported within the space above bottom plate 10and'underneath housing 12 by shaft 44. While shaft 44 may be supportedon the stationary frame in any suitable mannen'it is here shown asstationary and as;

7 being pressed at its upper end into stationary collar bracket 45,which is an integral part of: duct 31 at the forward end thereof.

' The drive member D comprises the circular plate 52 and-a central hub46 containing two spaced journal bearings 47 and 48 by which the hub 'isrotatably mounted upon the lower portion of fixed shaft 44. Thisconstruction is shown in greater detail in FIG. 2a. The lower 1 bearingsleeve43 is a press fit within hub 46, while the upper'end'of the hub at45a is stamped or crimped'over the upper edge of bearing sleeve 47 inorder to -holdthe bearing in the, hub. The hub and'bearing assembly isthen. prevented from'dropping offthe lower end of shaft 44'by washer 45*which is heldfin pl-ace by screw Sill Drive. plate 52is attached tohub&6 in any suitable manher as by pins 53 integralwitha flange 51' at thetop of' the hub, the pins being headed over to hold the gear plate inplace. Although other suitablev constructions maymbe "used, one is'tomake plate 52 froma thin sheet of steel 56 is able to. move rotationallyrelative to hub 46 as well as to move axially relativetothehub over a'limited range 5;

of. travel,'as will become apparent from further descrip tion. Sleevefie-is closed at its lower end and is there attached to brush plate. 570f surface working member Cl Brush plate 57 is a circular sheet of steelor other metal stamped to the proper size and shape and carryingunderneath a suitable polishing, or other surface working element 58engaging the floor or other surface being worked upon, such polishingelement here being shown in the form of a brush; but it will beunderstood that a cloth buffer, or abrasive, or other element may beused instead.

Sleeve 56 and plate 57 are non-rotatably connected to each other by anarrangement which is shown in detail in 'FIGS. 2a and 8. Sleeve 56 has aterminal boss 56a at its lower or outer end with a plurality of radiallugs 59. An opening in plate 57 has a corresponding number of radialnotches (57a in FIG. 2a) to receive the lugs 59. By engagement of lugs59 with the sides of the notches the sleeve and plate are drivinglyconnected. Lugs 59 are undercut near their bases to receive a springwire clip 59b which holds the plate against downward axial movementrelative to sleeve 56.

A driving inter-connection is effected between the drive member D, andthe surface working member C in order to rotate the latter, by meanswhich are shown in FIGS. 3 and 6 and will be described particularly inconnection with those figures. The inter-connecting means includes thecentrifugally responsive means comprising a pair of angular, weightedarms 60 pivotally mounted on the under surface of driver plate 52 bybolts 61 which are located at diametrically spaced positions on theplate. Each of the arms can move between an extreme inner position shownin FIG. 3 and an extreme outer position shown in FIG. 6 in response tothe balance of forces, including centrifugal forces, as is explainedlater.

Rigidly attached to each of the pivoted arms 60 is a gear segment 63,connection between the two being effected by means of the bolts whichprovide the pivots 61 and rectangular bosses on the arms fornon-rotatably connecting each gear segment 63 to the associated swingingarm so that the gear segments swing about pivots 61 in response toswinging movement of the arms.

On the exterior of sleeve 56 are gear teeth 64-. These gear teeth mayextend entirely around the sleeve if desired but it is adequate toprovide only a gear segment at each of two positions, as shown in FIGS.3 and 6 in which the teeth 64 mesh with the teeth of a gear segment 63mounted on an arm 60. It will be seen from a comparison of FIGS. 3 and 6that as arms 60 pivot about pivots 61, gear segments 63 meshing withteeth 64 cause sleeve 56 to rotate relative to driver hub 46. Thisrotation of sleeve 56, indicated in FIG. 6 by arrow 65, is about theaxis of shaft 44.- and is relative to the hub 46 upon which the gearplate 52 and the cent-rifugal'ly responsive elements 60 are mounted.

It will be seen from this construction that as gear plate 52 rotates,counter-clockwise, as indicated by arrow 70 in FIG. 3, the engagement ofthe teeth of segments 63 with teeth 64 on the outside of sleeve 56causes sleeve 56 to be carried around the axis of shaft 44 in unisonwith the drive member D.

Cooperating cam surfaces are provided on the drive member D and thesurface working member C to press the surface working member downwardlytoward the floor surface with a variable force depending on thespeed-induced force exerted by centrifugal weights 60 and the opposingtorque from the surface working member. These cooperating elements arebest understood by reference to FIGS. 2a, 4, 5 and 7. As shownparticularly' in FIG. 5, driver hub 26 is provided with two recesses 66at opposite sides of the cylindrical portion of the hub. At the upperend of each recess is a downwardly facing helically inclined surface 67.On the inside of sleeve 56 there are two inward projections 68 atdiametrically spaced positions. At the upper end of each projection isan upwardly facing helically inclined surface 69. A projection 63 fitswithin each of the recesses 67 as indicated diagrammatically in FIG. 4bringing the two surfaces 67 and 69 into engagement as shown in thatfigure. It will be noted that the two surfaces '67 and 69 are inclinedwith respect to the common axis of rotation of the hub and sleeve. Suchinclination is forwardly and downwardly with respect to the direction ofrotation (indicated by the arrows in the figures) for reasons which willbe further explained. It will be noted that a recess 66 is wider thanthe projection 68 in the recess, thus allowing for limited relativerotational movement of the driving hub and the surrounding sleeve, suchmotion be ing preferably limited in each direction by engagement of thevertical or axially extending edges of the recess and projection onthese two members. The limited extent of this relative rotation is shownby comparison of FIGS. 4 and 7 from which it will be seen that, as aresult of the relative rotation and the inclination of the surfaces 67and 69', there is also an axially directed component of motion causingrelative axial movement of the hub and surrounding sleeve.

When placed on a floor, brush 11 supports the whole device, typicallyweighing about seven or eight pounds. The surface working unit, free todrop down under its own small weight of about one pound, rests on thefloor. When the device is picked up the working unit is kept fromdropping off by flange 56b of sleeve 56 resting on gear segments 63.

In operation, the unit is connected to a vacuum cleaner by aconventional vacuum cleaner wand and hose, not shown in the drawing,which is inserted into the movable section 32 of the exhaust air duct.The vacuum cleaner motor is then started to create by suction a flow ofair through the floor polisher. The air entering through air intake 27passes into the space within housing 12 and then enters the turbinethrough the spaces between stationary vanes 25, causing turbine wheel 22to turn at a high speed.

Rotational movement is imparted to the drive member D from the turbineby teeth 40 on the drive pinion meshing with teeth 41 on the drivemember. It will be seen from the difference in the diameters of thedrive pinion and the drive member D that a substantial gear reduction isobtained. In a typical design the gear ratio is approximately 18 to 1.Thus if the turbine under an average load turns with a speed in theneighborhood of 15,000 or 16,000 r.p.m., the drive member D, and alsothe surface working member C, are rotated at speeds in the neighborhoodof 800-900 r.p.m. These figures are given merely as examples and theyare not limitative on the invention since exact speeds depend upon manyfactors, including the load imposed upon the surface working member, therate at which air passes through the air turbine, and many other factorsof design.

As drive member D rotates about shaft 44, the surface working member Cis rotated about the same axis at the same speed. A driving connectionbetween these two members is effected by the intermeshing of the gearsegments 63 with the gear teeth 64 on sleeve 56. Neglecting for themoment any rotational movement of the gear segments about pivots 61, itwill be seen that, assuming a fixed position of the segments and arms60, rotational movement of the gear plate 52 is transmitted through pins61 and segments 63 to sleeve 56 which in turn rotates plate 57 carryingbrush 58.

Superimposed upon this rotative motion is the effect of the movement ofarms 60 about pivots 61, these arms being responsive to the balance ofcentrifugal force and the reaction force exerted through the teeth insegments 63.

When the parts are stationary, arms 66 may occupy any position, but fordescriptive purposes may be assumed to occupy an inward position such asshown in FIG. 3. As the rotational speed of the drive member increases,the centrifugal force acting on these arms increases and tends to movethem outwardly, reaching an equilibrium position determined by a balancebetween centrifugal force tending to pull them out, and brush torque andthe torque reaction of the inclined cams acting through teeth insegments 63 tending to pull them in. ,The rotational movement ofarms 69around their pivots 61 causes equalrotational movement of gear segments63 about thesepivots. Such rota-;

tional movement ofthe gear segments causesj angular movement of sleeve56aboutvtheaxissof shaft .44 relative to hub 46. The brush, .by thecentrifugalaction, is pressed into floor contact With a workingpressure, typically about five pounds, which is materially greater thanthe dead weight of surface working element ,C, typically about onepound.

. 7 When the floor polisher is in operation, the drive, member D and thesurface working member Care rotated;

together in a counter-clockwise direction when viewed from above as inFIGS. 3 and 6. In FIGS. 4 and.7 the rotation is to the right. It will,be seen from comparison of FIGS. 3 and 6 that the outward swingingmovement of c'entrifugally responsive arms 66 causes sleeve 56 to.

advance v(arrow 65) in thevdirection of rotation relative to hub 46.,Presuming FIG. 4 represents the relative. p0si-.

tionof the hub and sleeve when the parts are stationary and brush 58 ismerely resting on the floor and is raising the surface working membertowardthe limit of its upplay no part in the driving connection betweendriver 'D j and surface working member .C.

It will ,be seen that the driving force. .advancing the cause of theinclination of the engaging surfaces 67 and 69 relative to the axis ofrotation. As thecentrifugallyresponsive arms 60 cause the sleeve toadvance angularly sleeve. with respectto the hubalso forces the surface,working member downwardly with respect to the hub be.

with respect to the hubon which the sleevevis, mounted,

the twocamfaces 67 and 690m. these members at the same time cause theaxial movement of the surface work? ing member in a downward direction.

The operative mode of the described device may b est be understood byfirst assuming it to be operating ata given fixed rotational speed withthe centrifugal fly weights at equilibrium in some intermediateposition. The mounting sleeve and the brush will then be in equilibriumunder the following forces:

(1) Axial upward force on the, brush;

'(2) Drag torque'on the brush opposing rotation;

(3) Torque from the centrifugally actuated fly weights in thedirectionof rotation;

4) Axial downward forcecomponent from the cam that inter-relates thedriving hub and the brush sleeve; (5) The torque tion.

Assume that the coeificient of friction between the component from thatcam Opposing rotabrushand floor increases substantially. Torque (3) fromthe centrifugalfly weights will remain constant at the constantlymaintained speed. Torque '(2)the drag torque on the brush-will increasewith the increased c0- efiicient of friction. Consequently torque '(5)the cam componenfopposing relative forward rotation of the sleeve on thedriver-must decrease to maintain equilibrium of moments. Torque (5) is atangential component of the'cam force. Thus the total cam force,including component (4) the downward force on the brush that pushes thebrush againstthe floor, has been reduced by an. 1 increase incoeflicient of friction between brush and floor even thoughthe speed hasbeen assumed to be constant. 7 It can be seen that this reduction indownward force on the brush is a direct result of coefiicient offriction increase andiis not a result .of speedLreductioh, Because ofthis reduction in downward force on the brush, the torque increase is:less than efiicient of frictionv. V I

Consider nowthat the actual polisher is driven by an air turbine, a typeof motor that has inherently poor speed regulation. Theneven the limitedtorque increase resulting from a substantial coeflicieutof frictionincrease will result in a significant reduction inrotational speed.However, any reduction in rotational speedrapidlyreduces thecentrifugalforce acting on the flyweights, and this reduction in force furtherreduces the downward force on 1 the brush. Thus the force with which thebrush contacts 3 the floor is responsive to both-changes in coeflicientof friction and rotational speed. Because ofthis combined action, arelatively large increase in'coefiicient of friction requires a verysmall reduction in rotational speed to re- 7 establish equilibriumconditions. 1

Also, the centrifugal portion-of the brush control takes care ofvariations in the air motor'powe-r due e.g., to varying vacuum cleanerconditions. If, for instance, that air motor power -is reduced, thespeed reduction, through the action of the centrifugal control, reducestorque (2) the drag torque on the brushand thus reduces the requireddriving torque, preventing the device from slowing excessivelyorstalling.

Considering the over-all functioning of the device it" may be noted,disregarding frictional-and other losses, that in general the dragtorque on the brush equals the driving torque from the motor. Thedownward pressure applied to the brush, and by it to the'fioor inaddition to its own light or effectively non-existent weight, is afunction-of the centrifugal force developed by thecentrifugal flyweights, which in turn is a function of the rotary speed and the brushdrag'torque. If, for any reason such as decreaseof torque from the motoror increase of torque drag on the brush, the rotating speed is lowered,the can tn'fugally developed down pressure on the brush decreases andputs the ,whole system in equilibrium 'as above'fexplained. The oppositeaction occurs to equilibratethe system if for any reason the rotatingspeed increases.

Seeing that the brush is only pressed downwardly into working pressureby operation of the device as'above explained, it. does not have toinitially contact the floor ,at

all, but can normally be held up to'its highest position (FIG. 2a).clear of the floor, by e.g., a light spring that preferably justsupports the weight of the brush unit.

I claim: A 1. In a surface working machine, the combination comprising:

a frame adapted to be supported at substantially fixed distance from asurface-to be Worked; a variable speed motor mounted on the frame; adrive member rotatably mounted on the frame on 'anaxis perpendicular tothe surface and driven in a'- forward direction b the motor; a

a surface working member rotatably mounted coaxially of the drive memberfor limited axial movement rela--- j tive thereto through a continuousseries of-working positions between a relieved position not more than Vlightly engaging the'surface and a fully engaged posi- 7 tion forciblyengagingvthe surface; meanscoupling the surface working memberrotatively tothe drive member, said coupling means permitting limitedrelative rotation of said two members; 7 means including cooperatingelements on the drive member and on the surface working member andacting tomove thesurf ace working member axially to-' ward saidfullyengaged position in response to forward rotationof thesurfaceworking member relative to the drive member, and centrifugallyresponsive mechanism interconnecting said members and acting to producea torque between said members in a direction to produce forward rotationof the surface working member relative to the proportional to theincrease in so drive member, said torque increasing with increasingrotational speed of said members,

whereby the surface working member is pressed on the surface to beworked with a force that increases with increasing rotational speed ofthe members.

2. In a surface working machine, the combination defined by claim 1, andwherein said centrifugally responsive mechanism comprises a plurality ofcentrifugal masses pivotally mounted at angularly spaced positions onone of said members for swinging movement relative to said one member ina radially outward direction with respect to said axis in response toincreasing member rotation,

and linkage means interconnecting said masses and the other member andacting to produce forward rotation of the surface working memberrelative to the drive member in response to radially outward swingingmovement of the masses.

3. In a surface Working machine, the combination de fined by claim '1,and wherein said centrifugally responsive mechanism comprises aplurality of gear segments pivotally mounted on one of said members at'angularly spaced positions and engaging gear teeth mounted coaxially onthe other member,

an equal plurality of centrifugal means mounted on said one member forradially outward movement relative thereto in response to increasingmember rotation,

and means interconnecting the centrifugal means with respective gearsegments to drive the gear segments in a direction to produce forwardrotation of the surface working member relative to the drive member inresponse to said outward movement of the centrifugal means.

4. In a surface working machine, the combination defined by claim 1, andwherein said centrifugally responsive mechanism exerts substantiallyzero torque between the members at zero rotational speed thereof,

and the only force then pressing the surface working member on thesurface to be worked corresponds substantially to the weight of thesurface working member.

5. In a surface working machine having a frame, the

combination comprising:

a variable speed motor mounted on the frame;

a drive member rotatably mounted on the frame and driven by the motor;

a surface working member rotatively connected with the drive memberconcentrically thereof to rotate therewith and for limited rotative andaxial movements relative to the drive member, said axial movement in onedirection being toward the working surface;

centrifugally responsive elements mounted on the drive member forrotation therewith and for movement to different positions relativethereto in response to different centrifugal forces at differentrotational speeds of the drive member,

the centrifugally responsive elements comprising arms pivoted near oneend to the drive member at angularly spaced positions, said arms beingweighted at their free ends to tend to swing outwardly as the speed ofthe drive member increases;

means connecting the centrifugally responsive elements to the surfaceworking member to rotate the surface working member and the drive memberin unison and also to rotate the surface working member relative to thedrive member in response to speed induced movements of the centrifugallyresponsive elements relative to the drive member,

the connecting means interconnecting said swinging arms directly withthe surface working member and including a sleeve connected to thesurface working member and journaled on the drive member and a gearsegment on the inner end of each arm meshing with gear teeth on saidsleeve;

and means including cooperating elements on the drive member and surfaceworking member acting to move the surface working member axially towardthe working surface as a result of said relative rotational movement ofthe surface working member caused by movement of the centrifugallyresponsive element due to higher rotational speeds.

whereby the surface working member is pressed on the working surfacewith a force generated by said centrifugally responsive elements andvarying with the rotational speed of the drive member.

6. In a surface working machine, the combination comprising:

a frame;

an enclosure for the frame including an upper cover and a bottom closureplate secured to the frame;

means supporting the machine on a working surface including a supportingbrush extending downwardly from the closure plate;

a rotational driver rotatably mounted on the frame within the enclosureto revolve about an axis normal to the working surface and having adownwardly projecting hub;

a variable speed motor mounted on the frame within the enclosure anddrivingly connected to the rotational driver,

a rotatable surface working member located below the bottom closureplate and having an upwardly projecting sleeve surrounding said driverhub for relative rotational and axial movements relative thereto andextending through the closure plate;

centrifugally responsive means comprising arms pivoted near one end tothe driver at angularly spaced positions, said arms being weighted attheir free ends to tend to swing outwardly as the rotational speed ofthe driver increases, and a gear segment on the inner end of each armmeshing with gear teeth on said sleeve;

and means moving the surface working member axially toward the workingsurface as a result of relative rotation of the driver and the surfaceworking member, said last mentioned means including mutually engagingcam surfaces on the driver hub and the sleeve of the surface workingmember, said cam surfaces being inclined toward the working surface inthe direction of rotation of the surface working member.

References Cited in the file of this patent UNITED STATES PATENTS2,609,555 Anderson Sept. 9, 1952 2,716,724 Burian Aug. 30, 19552,730,219 Kitto Jan. 10, 1956 2,967,314 Kowalewski Jan. 10, 1961

1. IN A SURFACE WORKING MACHINE, THE COMBINATION COMPRISING: A FRAMEADAPTED TO BE SUPPORTED AT SUBSTANTIALLY FIXED DISTANCE FROM A SURFACETO BE WORKED; A VARIABLE SPEED MOTOR MOUNTED ON THE FRAME; A DRIVEMEMBER ROTATABLY MOUNTED ON THE FRAME ON AN AXIS PERPENDICULAR TO THESURFACE AND DRIVEN IN A FORWARD DIRECTION BY THE MOTOR; A SURFACEWORKING MEMBER ROTATABLY MOUNTED COAXIALLY OF THE DRIVE MEMBER FORLIMITED AXIAL MOVEMENT RELATIVE THERETO THROUGH A CONTINUOUS SERIES OFWORKING POSITIONS BETWEEN A RELIEVED POSITION NOT MORE THAN LIGHTLYENGAGING THE SURFACE AND A FULLY ENGAGED POSITION FORCIBLY ENGAGING THESURFACE; MEANS COUPLING THE SURFACE WORKING MEMBER ROTATIVELY TO THEDRIVE MEMBER, SAID COUPLING MEANS PERMITTING LIMITED RELATIVE ROTATIONOF SAID TWO MEMBERS; MEANS INCLUDING COOPERATING ELEMENTS ON THE DRIVEMEMBER AND ON THE SURFACE WORKING MEMBER AND ACTING TO MOVE THE SURFACEWORKING MEMBER AXIALLY TOWARD SAID FULLY ENGAGED POSITION IN RESPONSE TOFORWARD ROTATION OF THE SURFACE WORKING MEMBER RELATIVE TO THE DRIVEMEMBER, AND CENTRIFUGALLY RESPONSIVE MECHANISM INTERCONNECTING SAIDMEMBERS AND ACTING TO PRODUCE A TORQUE BETWEEN SAID MEMBERS IN ADIRECTION TO PRODUCE FORWARD ROTATION OF THE SURFACE WORKING MEMBERRELATIVE TO THE DRIVE MEMBER, SAID TORQUE INCREASING WITH INCREASINGROTATIONAL SPEED OF SAID MEMBERS, WHEREBY THE SURFACE WORKING MEMBER ISPRESSED ON THE SURFACE TO BE WORKED WITH A FORCE THAT INCREASES WITHINCREASING ROTATIONAL SPEED OF THE MEMBERS.